Doesnt say the militia was meant to repel just indians and Mexicans. It may have been used to repel those groups, because they were needed for them.
My reading suggests anybody, like the Japanese during WWII if they had invaded America.
“You cannot invade America. If you do, there will be a rifle behind every blade of grass.”
Cueing “Yamamoto never said that!!!” in 5..4..3..2..1....